The Br azilian won 25 trophies with Los Blancos.
After 16 seasons at the Estadio Santiago Bernabeu, Marcelo received farewell messages from a number of generations of Real Madrid players, including Cristiano Ronaldo.
The pair were clinical down the left flank in some of the most successful years in the club's history, and the current Manchester United ace sent an emotional note to Marcelo.
"More than a teammate, a brother that football gave me," Ronaldo posted.
"On and off the pitch, one of the greatest stars with whom I had the pleasure of sharing a dressing room. Go for it all in this new adventure, Marcelo!"
Other messages included former team-mates and captains, with Marcelo having donned the armband for his final season at the club.
"You arrived as a child. How many times I shouted " Marcelooooo, come back " Thank you for being such a legend. A big hug my friend and all the best for the future," Iker Casillas shared on social media.
His compatriots from Br azil also had their say, including those who will lead the next generation, as well as other current team-mates.
" Marcelo! Thanks for everything! Legend as the player with the most titles at the best club in the world," Vincius Junior said.
"It was a pleasure to play and learn from you. Monster inside and outside. Eternal 12."
"I can say that I have played with the best left-back of all time," Toni Kroos posted.
Having played alongside iconic Real Madrid figures, messages from stars like Cristiano have made Marcelo's farewell all the more emotional.